1. Field of the Invention
This invention relates to the measurement of pupillary threshold response in the eye.
2. Description of the Prior Art
One of the major problems facing the ophthalmologist today is how to detect blinding eye disease early, decide on the cause, and institute treatment before significant visual loss occurs. Many of the conditions affecting the optic nerve and retina are treatable; these include glaucoma, compressive optic neuropathy (from tumors, aneurysms, or Graves Disease), pseudotumor cerebri (idiopathic intracranial hypertension), proliferative diabetic retinopathy, retinal detachment, and forms of aging macular degeneration.
Unfortunately, the present methods available for screening for these diseases are not very satisfactory. Patients with early eye disease are frequently asymptomatic and their diagnosis is often dependent upon a careful ophthalmologic examination. Even then, early signs may go undetected. Difficult and time consuming tests of visual function are often necessary to make the correct diagnosis, but they too can be normal early in the disease process. Furthermore, important tests of visual function, such as those that assess visual acuity, visual fields, color vision, and contrast sensitivity are typically subjective in nature. In addition, many patients are not capable of accurately responding to subjective test measurements, as their judgment is often so clouded by their fears of blindness that their responses tend to be unreliable. Thus, visual tests which are based upon subjective measurement are inherently lacking in accuracy or reliability.
Wherefore, there is a need for an improved system for assessing visual loss that is more objective, efficient and reliable. This invention makes use of an objective neuronal reflex, the movement of the eye's pupil in response to light stimuli, in order to better assess visual function. Computerized methods of providing carefully controlled light stimuli and precise recording of pupil movements in response to light are used to quantify the pupillary light reflex. The present invention uses new methods to determine the threshold light intensity needed for a pupillary response (pupil threshold). The system of the present invention is based upon objective rather than subjective measurements, can be completed in a short period of time, and provides accurate and reliable results.